function SceneBuilder(webglObj){
	
	var _webgl = webglObj;
	var _repSceneWrappers = {};//mantiene un repositorio de wrappers creados
	
	this.generateScene = function(sceneName){
		
		if (_repSceneWrappers[sceneName]){return _repSceneWrappers[sceneName];}
		
		var generatedScene = null;
		switch(sceneName){
			case "Alem_Fly":
				generatedScene = new AlemScene(webglObj);
				break;
				
			case "Alem_1stPerson": 
				generatedScene = new FirstPersonScene(webglObj);
				break;
				
			default: 
				sceneName = "default";
				if (_repSceneWrappers[sceneName]) {generatedScene = _repSceneWrappers[sceneName];}
				generatedScene =  new DefaultScene(webglObj);
		}
		
		_repSceneWrappers[sceneName] = generatedScene;
		return generatedScene;
	}
	
};